Enjoy that 34 gallon cup of coffee

Many years ago, the mighty Colorado River quit reaching the Sea of Cortez, petering out south of the Imperial Valley. I thought of the Colorado as I read about virtual water, the concept of Professor John Anthony Allan of the University of London. Virtual water is, in a nutshell, the total amount of water needed to produce a good, including irrigation, packaging, shipping and retailing. For example, he calculates the cup of Café Americano at my elbow took 34 gallons of water to create.

Living near the Great Lakes, I've never been concerned about the availability of fresh water, but for much of the world it is the most precious commodity. The concept helps illuminate the relative ecological burden of our agriculture. For example, according to the World Water Council, to growing 1 kg of beef takes almost 15 times as much water as 1 kg of wheat. 100 grams of ground beef contains 259 calories, while 100 grams of ground wheat flour contains almost 400 calories. We pay a high virtual water price for our tasty, tasty burgers.

A UNESCO study found some eye-opening virtual water hogs; to create a pair of jeans requires 10,850 liters; a diaper, 810 liters; and a bed sheet, almost 10,000 liters. A typical swimming pool holds about 350 pairs of jeans' worth of water.

The idea becomes important when it pinpoints places where too much use of virtual water by one group impacts its availability for others. Mexican farmers along the Colorado is a good example. India is another; just look at the brouhaha Pepsi has experienced from locals convinced its water usage has created a shortage.

As the idea of carbon offsets gains traction, don't be surprised if the idea doesn't spread to virtual water. Going green may require us to think blue.